This is part of a new series I am starting on the blog where we’ll explore RISC-V by breaking down real programs and explaining how they work. You can view all posts in this series on the RISC-V Bytes page.
When looking at the generated assembly for a function, you may have noticed that the first few instructions involve moving values from registers to the stack, then loading those values back into the same registers before returning. In this post we’ll explore why this is happening, why certain registers are used, and how behavior guarantees make life easier for compiler authors and enable software portability.